The invention relates to an endoscope and, more particularly, to an endoscope provided with an electronic components such as a solid-state image sensor at a distal end of the insertion section.
Recently, developments of multi-functional, electronic endoscopes are in progress. For instance, an endoscope with a solid-state image sensor as observing means has been provided. The endoscope with a solid-state image sensor or like electronic component should be assembled carefully. In a prior art method of assembly, a channel tube, liquid and gas supply tubes, etc. are assembled at the distal end of the insertion section of the endoscope, and then an objective lens and the solid-state image sensor are assembled at the distal end. A lightguide or the like is also mounted in the distal end portion before or after the mounting of the solid-state image sensor. This assembly requires an extremely clean environment to avoid attachment of dust to the image sensing surface of the image sensor and also a charging countermeasure to avoid rupture of the image sensor due to static electricity. However, it is infeasible from the standpoint of equipment cost to provide the environment and countermeasure noted above for the entire process of assembly of the endoscope.
Since solid-state lubricant is greatly used in the process of assembling the endoscope, it is necessary to vary the operating environment for each-assembling step. Further, the disassembly and repair of the endoscope require operating environments with dust and static electricity countermeasures. It is impossible from the cost stand point to install repair factories with such equipment throughout Japan or all over the world, that is, the number of such repair factories is limited. Therefore, once there occurs a trouble in the endoscope, it takes considerable time to transport the endoscope to the repair factory and make repair.
Further, the solid-state image sensor is mounted in the distal end portion after the channel tube, liquid and gas supply tubes, etc. are assembled. Therefore, it is difficult to make accurate focus adjustment of the image sensor. Further, it is difficult to shield and insulate the image sensor or make shield and insulation tests. Naturally, the reliability of such shield and insulation is inferior.